Continuation of work in progress is focussed on two problems: (1) synthesis, assembly, and function of bacteriophage T4 short tail fibers (the product of gene 12), including the role of gene 57 in the assembly of active 12P; (2) the molecular mechanisms of the shutoff of host and early viral transcription in T7 infection, known to require the T7 gene 0.7 product. The new program involves bacteriophage 06, active on Psedomonas phaseolicola. This virus contains, among other novel features, double-stranded RNA. We intend to isolate conditional lethal mutants of 06 for the purpose of studying genetic recombination and/or reassortment in an RNA virus.